Generally, an appearance of a surgical handpiece has a handgun-shaped structure, and a pneumatic motor is generally used as a driving power source of the handpiece. The handpiece has a structure in which the rotational force of the pneumatic motor is applied to a cutting tool (drill) through a gear assembly. Also, it is necessary to rotate a bur or drill mounted on the handpiece in a reverse direction by shifting the rotational direction of the pneumatic motor during surgery.
When describing techniques capable of shifting the rotational direction of the pneumatic motor, Korean Patent Publication No. 10-2014-0133934 relates to a surgical system including an electric rotary handpiece. The surgical system includes a surgical handpiece having a housing having a grip and a driving shaft rotatably held by the housing; a trigger assembly configured to generate a signal representing a user's desired speed, in which the trigger includes a trigger held by the grip; and a mode selection assembly configured to generate a signal representing a user's desired rotational direction, which includes a collar held by a housing adjacent to the grip, in which the handpiece is configured so that the index finger of the user's palm may selectively interact with the trigger and the collar when the grip is gripped in the palm of a user's hand. The technique has a mode selection assembly for changing the rotational direction, but there is a problem in that the structure is complicated and it is difficult to manufacture.
Further, Korean Patent Registration No. 10-0549101 relates to a surgical punching drill including: a drill body having a handgun-shaped structure and a drill chuck driven by a pneumatic motor, in which the drill body has a valve mounting portion vertically formed inside a grip, a motor mounting portion formed at the inner rear end of a head portion, and a gear mounting portion formed at the inner front end of the head portion of the drill body, the motor mounting portion is mounted with a pneumatic motor and the valve mounting portion is mounted with a valve assembly for providing a gas flow path through which gas input from a gas source is transferred to the pneumatic motor and controlling the gas flow on the gas flow path, a trigger member for controlling the gas flow path by operating the valve assembly is provided at an upper end of the valve assembly, the gear mounting portion is mounted with a gear assembly for rotating a drill chuck by receiving a rotational force through a shaft coupled to the pneumatic motor, only the valve assembly that does not cause heat generation is mounted on the grip of the drill body, and the pneumatic motor is mounted on the head portion of the drill body, thereby preventing the grip from being heated. The technique has a simple structure, but does not provide a technique for shifting the direction of the drill.